Azo-Functionalized Zr-MOF and Its Mixed Matrix Membrane for High-Capacity Adsorption of Organic Dyes in Water

The efficient removal of toxic organic dyes from wastewater is of great significance in water pollution remediation. In this work, an azo-functionalized Zr-MOF (UiO-67-BCDC) was successfully designed and synthesized. The successful modification of azo groups enables the formation of broader π-conjugated electron systems, thereby strengthening the π-π interactions between the MOF and dye molecules consisting of π-rich conjugated aromatic systems. UiO-67-BCDC achieves over 90% removal efficiency for small molecule dyes within 10 min. Under aqueous conditions at 313 K and pH =  7, optimal adsorption performance was achieved at an adsorbent dosage of 0.50 g/L, resulting in an adsorption capacity of 710.27 mg/g for Basic Blue 3 (BB-3). The maximum adsorption capacity of UiO-67-BCDC toward BB-3 is 621.68 mg/g at 303 K, approximately 1.2 times that of UiO-67. To prevent agglomeration and loss of powdery MOFs, the UiO-67-BCDC@SA membrane was made with sodium alginate (SA), achieving a BB-3 adsorption capacity of 507.04 mg/g. This study demonstrates an effective strategy for dye removal by azo functionalization and membranization, producing a high-capacity adsorbent with exceptional performance.